Low expansion alloy



United States atent LOW EXPANSION ALLOY Werner Kster and Eberhard Braun, Stuttgart, Germany, assignors to Metals & Controls Corporation, Attleboro, Mass., a corporation of Massachusetts Application February 11, 19515, Serial No. 487,645

Claims. (Cl. 75-134) This invention relates to metallic alloys of the kind having extremely small temperature coefficients of expansion, and in particular to alloys of this general class which can be used as the low expansion side of thermostat metals.

Among the several objects of the invention, therefore, may be noted the provision of an alloy having a low temperature coeicient of expansion; the provision of an alloy of this specific class which is of such nature that it can be bonded to known alloys having relatively high temperature coeflicients of expansion; the provision of alloys of the above types which do not require nickel as a constituent; and the provision of such alloys which are relatively economical to make. Other objects and advantages will be in part obvious and in part pointed out hereinafter.

In the drawings which accompany this application, Fig. l shows a phase diagram, and illustrates therein the range in which the constituents of the alloy of this invention may be chosen. Fig. 2 presents dilatometer curves showing the expansions of two embodiments of the i11- vention for dilerent temperatures.

In the manufacture of thermostat metal, it is customary to use as one side thereof a metal which has a very low temperature coeicient of expansion. The best known alloys of this type are the iron-nickel alloys having a nickel content in the order of 36%; and of these ironnickel alloys, that one known as Invar is the most widely recognized, this alloy containing 36% nickel. However, in times `of war it is generally dicult to obtain nickel for non-war purposes, and thus the manufacture of thermostat metal for non-war devices is seriously restricted. For this reason, there has been much searching done for an alloy which does not contain nickel, and yet which has a relatively low temperature coelicient of expan sion. Up to now, no such alloy has been konwn.

However, itis herein now disclosed that the manganeseantimony-arsenic alloys do have the necessary low temperature coeilcient of expansion, and can be used for the low expansion side of thermostat metal.

The composition of the alloys of this invention can be determined from the cross-hatched area of the alloy diagram in the accompanying drawing. In these alloys, the following proportions give the ranges of each con stituent:

Percent by weight Manganese 29-41 Antimony 34-69 Arsenic 2-25 ice to use. However, since in some instances it is not the most economical thing to produce alloys lying exactly on this line, the cross-hatched area is given to show the permissible ranges of the various constituents.

It has been found that the expansion coefficient of alloys lying within the cross-hatched area is extremely small and comparable to the expansion coefficient of the iron-nickel alloys with approximately 36% nickel. For example (as shown in Fig. 2), the expansion coeftcient of an alloy with 31.1% manganese, 63.8% antimony, and 5.1% arsenic amounts to l0.58 10s for heating between -50 and +150 C., and -l.5 l06 for cooling. This is shown as curves 4 and 6 of Fig. 2, curve 4 being for heating and curve 6 being for cooling.

As another example, an alloy having 35.4% manganese, 52.8% antimony, and 11.8% arsenic has a temperature coeicient of expansion of about the same value as that given above, in a range between and {-75 C. This is shown as curves 8 and 10 of Fig. 2, curve 8 being for heating and curve 10 for cooling.

The speciiied alloys are not subject to cold working except to a very small degree. Therefore, metals which are to be made therefrom preferably should be produced by casting or sintering, following standard techniques of melting and pouring, and/or sintering.

In connection with sintering, it is expedient to manufacture objects that are to be made from alloys according to this invention, by fritting together particles of these alloys by means of small quantities of metallic or nonmetallic binding agents. For this purpose, it is desirable to use binding agents having temperature coeicients lof expansion as close as possible, and as similar as possible, to those of the alloy. If the two expansion coeilcients (the one of the alloy and the one of the binding agent) di'ner greatly, then the quantity of the binding agent must be held to a minimum in order not to impair the expansion coefficient of the finished material.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above alloys without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawing, shall be interpreted as illustrative and not in a limiting sense.

We claim:

1. An alloy having a low temperature coeiicient of expansion consisting essentially of manganese, 29-41%, antimony, S14-69%, and arsenic, 2-25%, all by weight.

2. A low temperature coeicient of expansion alloy consisting essentially of manganese, 31.1%, antimony, 63.8%, and arsenic, 5.1%, all by weight.

3. A low temperature coefficient of expansion alloy consisting essentially of manganese, 35.4%, antimony, 52.8%, and arsenic, 11.8%, all by weight.

4. A sintered metallic composition in which the major powdered constituent comprises particles of an alloy containing manganese, 29-4l%, antimony, 34-69%, and arsenic, 2-25 all by weight Iof said alloy; and in which a minor constituent comprises a binding agent having a temperature coeflcient of expansion of the same order of4 magnitude as said major constituent.

5. A sintered metallic composition in which the major powdered constituent comprises particles Iof an alloy containing manganese, 29-41%, antimony, Sil-69%, and arsenic, 2-25%, all by weight of said alloy; and in which a minor constituent comprises a binding agent having a temperature coelicient of expansion approximately equal to that of said major constituent.

No references cited. 

1. AN ALLOY HAVING A LOW TEMPERATURE COEFFICIENT OF EXPANSION CONSISTING ESSENTIALLY OF MANGANESE, 29-41%, ANTIMONY, 34-69%, AND ARSENIC, 2-25%, ALL BY WEIGHT. 